Deodorizing of edible fats and oils is an important step in the refining process. One deodorizer design class includes a vacuum vessel containing a plurality of vertically stacked trays, in which the oil consecutively is transferred from tray to tray. A sub class of the tray-based deodorizer type is operating in semi-continuous mode where the batch of oil residing in a tray is kept as a separate entity during the transferring to other trays. This semi-continuous mode allows for stock change without interrupting the operation, but induces instantaneous and significant material temperature changes at the time of batch-switch.
In deodorizers of tray-based semi-continuous type the heating or cooling of the oil is suitably executed in dedicated trays where heat exchanging coils are arranged in zones for heating and cooling. The heat exchanger coils of the current state of art are either of helical or of serpentine design. The spiral coil design inevitably leads to an empty space in the centre, in which no heat transfer area exist, this is negatively affecting which total heat transfer surface area which can be installed. Furthermore, the structure of the heat exchanger is quite rigid, leading to material fatigue and eventually coil crack due to the thermally induced expansion or contraction derived from frequent switching of oil batches of different temperatures.